1. Field of the Invention
The present invention relates to a slide valve.
2. Description of the Related Art
When a vacuum pump, for example, a turbo-molecular pump is attached to a vacuum chamber of a vacuum processing apparatus, a slide valve is generally interposed therebetween.
A slide valve described in Patent Literature 1 (U.S. Pat. No. 5,577,707) adjusts the flow rate by allowing a slide plate to slide so as to be inserted into and removed from a flow channel. In order to bring the valve into a fully closed state, an annular sealing body provided with a seal ring is allowed to come into contact with the edge of the slide plate inserted into the flow channel to thereby block the flow channel.
The sealing body described in Patent Literature 1 includes the seal ring, an annular piston, and a plurality of bolts which connect the seal ring and the piston to each other, the bolts being arranged in the circumferential direction. The piston is driven by using a spring and compressed air to thereby allow the sealing body to come into contact with and separate from the slide plate.
Along with the operation of the valve, a shift in the positional relationship in the circumferential direction between a fixation part of the seal ring and a fixation part of the piston may occur. In the invention described in Patent Literature 1, a line connecting a fixation position on the seal ring to a fixation position on the piston of each of the bolts may not be parallel to a movement direction of the sealing body due to the above position shift. In this case, of course, the bolt is also not parallel to the movement direction of the sealing body.
An O-ring is disposed between the peripheral surface of each of the bolts and a wall surface of a space in which the bolt is housed. When the bolt is not parallel to the movement direction of the sealing body as described above, the O-ring have uneven contact, thereby deteriorating the sealability of the O-ring. As a result, compressed air or atmospheric air may leak toward a vacuum system or an operational failure caused by contact between the bolt and the wall surface around the bolt may occur. Thus, the performance as a slide valve cannot be ensured.